High voltage ignitron



Jan. 17, 1939. H KLEMPERER 2,144,496

HIGH VOLTAGE IGNITRON 7 Filed Jan. 15, 1938 1 V 7?) Supply sou rce.

WITNESSES: INVENTOR Hgns [(lemperen ATTORNEY Patented Jan. 17, 1939 UNITED STATES PATENT OFFICE HIGH VOLTAGE IGNITRON Pennsylvania Application January 13, 1938, Serial No. 184,837

5 Claims.

My invention relates to vapor electric converters, and more particularly to converters suitable for high voltage operation.

In the operation of vapor-electric converters, such, for example, as vapor-arc rectifiers employing a make-alive electrode which is in contact with the liquid metal cathode, a considerable amount of sputtering of the liquid cathode takes place during the initiation of a spark at the junction of the make-alive electrode and the surface of the cathode. I believe that the sputtered particles of cathode material sweep up into the arc path and impinge upon the anode of such devices. This condition is liable to have an adverse efiect upon the discharge of the rectifier in that short circuiting and allied phenomenon may occur to the detrimental effect of the rectiher and upon its operation.

Prior art devices of this character have somewhat reduced the destructive efl'ects of cathode material by reducing the size of the anode so that the anode becomes heated by the discharge current and the cathode particles are evaporated upon striking the anode. However, high voltage anodes must be constructed larger to avoid a large field strength at their surface. Other devices maintain a long distance path between the anode and the cathode with many interposed grids and shields. Such devices likewise are undesirable as the arc-drop is considerably increased and starting difliculties become more numerous.

According to my invention I eliminate the above mentioned difiiculties and disadvantages by interposing a metal plate between the anode and the cathode, which is heated practically red hot by some suitable source of current. Briefly, upon the formation of the cathode spot between the make-alive electrode and the cathode surface, the attendant blast sweeps globules of mercury up which are carried in with the arc formed between the cathode and the anode. I mount a disk-like plate or shield above the cathode which I maintain hot by passing a current through it in some suitable manner. The sputtered particles of mercury drops on their upward journey impinge upon the lower surface of the heated plate and evaporate instantaneously. The heat radiated to the anode from the upper side of the heated plate raises the temperature of the mercury vapor in the anode region. With superheated vapor in this region, a high vapor pressure is developed and the expansion of the vapor near the anode results in an outward movement of the vapor from a high pressure region towards the container walls, a region of substantially lower vapor pressure. Although the vapor pressure in the anode region is raised by the heat transferred, the vapor density is correspondingly decreased.

It is, therefore, an object of my invention to provide a heated disk-like plate between the anode and the cathode of vapor-arc rectiflers to evaporate mercury sputtered from the cathode during the initiation of the cathode spot.

It is another object of my invention to prevent backfires and reverse arcing within the rectifier during operation.

Still further, it is an object of my invention to heat the vapor in the anode region in order to reduce the vapor density thereabout.

Another object of my invention is to provide an improved construction of a vapor-arc rectifier capable of intercepting globules of mercury sputtered during operation and condensing the mercury thus intercepted before moving into the anode region.

Another object of my invention is to provide a disk-like plate between the anode and the cathode adapted to become heated quickly upon application of current.

Other objects and advantages of my invention will be apparent from the accompanying drawing, in which the single figure is an elevational view of an electric converter embodying my invention.

The apparatus according to my invention comprises an evacuated container 3 of glass or other suitable material having an anode 5 sealed therein, a cathode l of vaporizable reconstructing ma-' terial such as mercury and a suitable makealive electrode 9 in permanent contact with the cathode 1. Between the anode 5 and the cathode I, I mount a suitable disk-like plate H 'or shield preferably made of iron or some similar material. The plate ll extends over a substantial portion of the cathode I and is preferably located close to it.

Alternating current is supplied from some suitable source such as a. transformer I3, the direct current consuming device I5 being located between the transformer l3 and the anode 5. The make-alive electrode 9 is supplied by a suitable source of exciting potential such as a transformer H. In series with the make-alive electrode 9 is a suitable resistor IQ for controlling the current flowing to the make-alive electrode 9 and a unidirectional device 2| such as a copper oxide rectifier or an arc discharge tube adapted to permit current to flow to the makealive electrode 9 only during positive half cycles. it will be apparent those skilled in the art that The disk-like plate II is supplied with current for heating it from a suitable sourcev such as transformer II. A resistor 23 is inserted in series with the plate II to keep the current supplied within such limits that the plate H is not unduly overheated. Since the hot disk-like plate ll only protects the front side of the anode 5, a suitable shield 25 is provided which substantially covers the side portions or the anode 5.

In the operation or my device, alternating current is supplied to the main electrodes 5 and I oi the converter 21 from a transformer l3 while alternating current is supplied to the make-alive electrode 9 from another transformer 23. Positive potential will flow through the unidirectional conductor 2| to the make-alive electrode 9 whereupon a cathode spot forms at the junction of the make-alive electrode 5 and the mercury cathode I when the current exceeds a critical value. Simultaneously with passage of current to the make-alive electrode 9 from a suitable sourcesuch as a transformer l'l, current is also being supplied from the same source I1 to heat the disk-like plate II. The make-alive electrode 9 is connected in parallel with the plate II by a conductor 12 so that the make-alive electrode 9 and the plate II are kept positive at the same time. Under proper conditions of potential, the cathode spot immediately expands into an are which will transfer quickly to the plate II and then to the anode 5.

The are path between the cathode I and the anode 5 is maintained in an active state by a stream of electrons emitted from the cathode I and the blast accompanying the formation of the initial spark sweeps many droplets of mercury up and into the arc path. By interposing a disklike plate II in the arc path, the stream of electrons is deflected sidewise and then travel upward towards the anode 5. However, any mercury droplets carried by the arc stream would be immediately vaporized upon striking the heated plate II and the vaporized mercury would tend to spread out and expand upwardly throughout the rectifier container 3. Eventually this mercury vapor is condensed by the cool walls of the container 3 forming droplets of liquid mercury which would fiow back down to the cathode pool 1. Without the plate II, the impact of mercury droplets sputtered from the cathode 1 upon the anode 5 would virtually destroy the negative electrode reluctance, a condition favorable to reverse arcing and backfires.

In order to make the action of the hot-plate ll eflective, the plate II should be preferably thin in order toheat up quickly. danger in overheating the plate II by supplying excessive current to it. However, the resistor 23 limits the current in the neighborhood of six amperes. The container 3 must possess an adequately cooling surface and a large enough condensing area so that the heat radiated by the hot plate II does not raise the vapor density in the dangerous region.

According to my invention, the region about the lower surface of the anode 5 becomes heated by the hot plate so that with the increased temperature, the mercury vapor expands and is carried away from the anode region. The heat carried to the anode region is mainly by the process of convection and radiation.

For purposes of illustration, I have shown a specific embodiment of my invention. However,

There may be changes and modifications can be made therein without departing from the spirit of my invention or the scope of the appended claims.

I claim as my invention:

1. Ina vapor electric converter comprising an evacuated container, an anode, a vaporizable reconstructing cathode and a make-alive electrode in permanent contact with said cathode, a disclike plate interposed between said cathode and said anode, said plate being substantially close and parallel to said cathode, the power circuit for heating said shield being closed only during the conducting period or said converter, means comprising an external source of power for heating said plate.

2. In an electric discharge device comprising an evacuated envelope, an anode a vaporizable cathode and a starting electrode dipping into said cathode, means for vaporizing particles sputtered from said cathode before reaching said anode, said vaporizing means including a disc-' located above said cathode, a source of potential for heating said shield, said heated shield capable of evaporating sputtered particles of cathode material and in addition serving as an auxiliary anode during 'low voltage excitation of said discharge device with respect to said cathode during the conducting period of said discharge device.

4. In a vapor electric converter comprising an evacuated container, an anode, a cathode of vaporizable reconstructing material and a makealive electrode in permanent contact with said cathode, a disc-like plate interposed between said anode and said cathode, means for supplying potential simultaneously to said plate and said make-alive electrode, an unidirectional device connected in series with said make-alive electrode for preventing operation of said make-alive electrode during inverse half cycles and hence controlling the supply of potential to said plate,

. said plate adapted to be heated simultaneously with the initiation of a cathode spot on said cathode during conducting half cycleswhereby 5. In a vapor electric converter comprising an evacuated container, an anode, a cathode of vaporizable reconstructing material and a makealive electrode in permanent contact with said cathode, a disc-like plate interposed between said anode and said cathode, a source of potential for heating said plate, a current-limiting resistor in ductor in series with said starting electrode for rendering said make-alive electrode operative during conducting halt cycles whereby cathode material sputtered during the formation of said cathode spot is evaporated by said heated plate before reaching said anode.

HANS KLEMPERER. 

